The present invention relates to an image reading apparatus for reading an image of an original sheet, and more particularly, to an image reading apparatus enabling a long light source in the main scanning direction to be cooled uniformly.
In image reading apparatuses installed in copying machines, scanners, facsimiles and the like, generally, an original is irradiated with light, the reflected light is passed through lenses to form an image and applied to an image sensor such as a CCD and the like, the image sensor converts the image into electronic data, and the image data is thus obtained. In such an image reading apparatus, a halogen lamp, xenon lamp and the like have conventionally been used as a light source.
These lamps generate the large amount of emission, but have a defect of also generating the large amount of heat. As the lamp temperature increases, when an inverter for power supply is disposed near the lamp, there is the fear that an electronic component of the inverter cannot operate normally because of overheating and that life of the lamp decreases and cannot emit the light. Further, when the heat of the lamp is conducted to platen glass which a user contacts and the temperature of the platen glass increases to a predetermined temperature or more, another problem also arises in safety to the human body.
Particularly, in the case of the image reading apparatus using an automatic document feeder (ADF), the lamp is continued to emit the light for a long time to read a number of originals, and the temperature of the lamp increases excessively. In recent years, a larger amount of light has increasingly been required to enhance the reading speed of the image reading apparatus, and has remarkably increased the temperature of the lamp. Generally, in the image reading apparatus is used a rod-shaped lamp long in the main scanning direction, and when the temperature difference in the longitudinal direction of the light source increases, the amount of light emission becomes nonuniform in the main scanning direction for reading an original, and image data to acquire deteriorates. Further, when the temperature difference is large, another problem arises that the lamp is not lighted. Therefore, in cooling the lamp, such a consideration has been required that the temperature becomes uniform in the lamp long in the scanning direction.
Then, it is important to dissipate heat liberated from the lamp to suppress overheating of an optical reader apparatus containing an inverter. Therefore, various methods have conventionally been considered such as blowing air to the lamp using a fan to cool and the like. As a conventional lamp cooling method to uniform temperatures in the main scanning direction, for example, an image reading apparatus is disclosed in Patent Document 1 (Japanese Laid-Open Patent Publication No. H11-194701). In this apparatus, in order to uniform the cooling wind from blowing cooling means (cooling fan) in the main scanning direction, a second scanning section (second carriage) is provided with a fin that is deflection means of the cooling wind.
However, in the conventional image reading apparatus as shown in Patent Document 1, it is necessary to newly install a fin for deflecting the cooling wind from the cooling fan, and the problem arises that the cost increases because of an increase in the number of components.
In view of the above-mentioned conventional problem, it is an object of the invention to provide an image reading apparatus enabling a long light source inside the image reading apparatus to be uniformly cooled in the main scanning direction with a simplified structure without increasing the number of components.